At the beginning of the delivery phase, every user \(k \in {\mathcal {K}}\)  reveals its requested file \(W_k \equiv W(s_k)\) , i.e., \(W_k\)  depends on the state \(s_k\)  where user \(k\)  is located. The server then builds and transmits several nested codewordsHere we consider the NCM scheme [1]} to support multi-rate transmission. However, the scheme is oblivious to the modulation procedure and any other multi-rate modulation scheme may be used (e.g., [2]}, [3]}, [1]}, [5]})., such that after receiving the codewords, all the targeted users can reconstruct their requested files. User \(k\)  requires a total amount of one normalized data unit to reconstruct \(W_k\) , as detailed in Section . However, only a subset of this data, with size \(m_k \equiv m(s_k)\) , is available in its cache. Therefore, the remaining part should be delivered by the server. Note that the conventional multi-server CC-based delivery scheme, as used in [6]}, assumes all users have the same cache ratio. Hence, it does not apply to our considered scenario where each user has cached a different ratio of its requested file. Thus, a new delivery mechanism is required to achieve a proper multicasting gain.
